peer-reviewedThis study evaluated the nutritive value of three contrasting components of maize
stover (leaf, upper stem, lower stem) at three harvest dates. The leaf component had a
greater in vitro dry matter digestibility (DMD) and a lower NDF concentration, compared
to the stem components. Delaying harvest reduced the in vitro DMD of the stem
components to a greater extent than leaf, reflecting lower increases in the NDF and
lignin concentrations in leaf tissue. The stem components of maize stover had a lower
nutritive value than the leaf component, and had a larger decrease in digestibility with
delayed harvest.Funding for this study was provided under the
National Development Plan through the Research Stimulus fund administered by the Department of Agriculture, Food and the Marine (RSF 07 501

Doyle, Evelyn M.

Lynch, J.P.

O'Kiely, Padraig

Irish Journal of Agricultural and Food Research

English

T-Stór

205Irish Journal of Agricultural and Food Research 53: 205–211, 2014†Corresponding author: P. O’Kiely; E-mail: padraig.okiely@teagasc.ieA note on the chemical composition and in vitro digestibility of contrasting stover components of maize grown in climatically marginal conditions and harvested at differing maturitiesJ.P. Lynch1,2, P. O’Kiely1,† and E.M. Doyle21Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co. Meath, Ireland2Schools of Biology and Environmental Science, UCD, Belfield, Dublin 4, IrelandThis study evaluated the nutritive value of three contrasting components of maize stover (leaf, upper stem, lower stem) at three harvest dates. The leaf component had a greater in vitro dry matter digestibility (DMD) and a lower NDF concentration, com-pared to the stem components. Delaying harvest reduced the in vitro DMD of the stem components to a greater extent than leaf, reflecting lower increases in the NDF and lignin concentrations in leaf tissue. The stem components of maize stover had a lower nutritive value than the leaf component, and had a larger decrease in digestibility with delayed harvest.Keywords: harvest date; leaf; maize; stem; stoverIntroductionThe nutritive value of maize stover (total stem and leaves) is much lower than for the cob component (grain and rachis; Cook and Shinners 2011; Lascano and Heinrichs 2011), and generally supports similar rates of animal performance to what could be achieved with average qual-ity grass silage (O’Kiely and Moloney 1995). However, maize stover can con-tribute over 50% of the whole-crop dry matter (DM) yield and changes in the chemical composition of maize stover dur-ing the later stages of crop development have a large impact on the whole-crop nutritive value(Lynch, O’Kiely and Doyle 2012, 2013). Recent interest in the poten-tial of dual-purpose maize varieties to 206     IRISH JOURNAL OF AGRICULTURAL AND FOOD RESEARCH, VOL. 53, NO. 2, 2014improve the overall efficiency of maize production systems (Blümmel, Grings and Erenstein 2013; Erenstein, Blümmeland Grings 2013) highlights the importance of understanding how crop management affects the stover component of maize. Such information is not readily available, particularly for crops grown under tem-perate but marginal conditions for crop growth and cob development.Furthermore, stover consists of contrast-ing components, such as the leaf and the stem (Tolera and Sundstøl 1999; Tang et al. 2006). Knowledge of the detailed chemical composition and nutritive value of these individual components at various stages of maturity provides a basis for determin-ing opportunities to improve the value of stover to whole-crop maize production. However, very little information is avail-able on these maize stover components produced in climates that are marginal for maize growth due to insufficiently high temperatures during the growing season. The objectives of this study were to deter-mine the effects of harvest date and stover fraction on the chemical composition and in vitro digestibility of maize stover.Materials and MethodsCrop production and managementThe maize cultivar Andante (Groupe Limagrain, Chappes, France) was sown under transparent plastic mulch (137 cm wide, 6 micron thick film, which covered two rows of seed; X-tend transparent pho-todegradable polythene, I.P Ltd., Gorey, Co. Wexford) at Grange, Dunsany, Co. Meath (53°30′ N, 6°39′ W and 83 m above sea level) on 2 April 2009 using a Samco 4 Row 4700 SP seed drill at a depth of approximately 5 cm and at a rate of 100,000 seeds per hectare. This cultivar had achieved a high cob propor-tion (> 500 g/kg whole-crop) and starch concentration (180–250 g/kg whole-crop DM) in previous trials at the same site (Lynch et al. 2012, 2013). Cattle slurry was applied to all plots prior to plough-ing, at a rate calculated to provide 33 kg available N/ha. Inorganic N was applied at 135 kg N/ha in the form of calcium ammonium nitrate (CAN; 275 g N/kg) 4 h prior to sowing. For each of three repli-cate blocks of a split-plot design, three harvest date treatments (7 September, 5 October and 5 November) were randomly allocated among three main plots, within which sub-plots were randomly allocated to one of three stover components. Thus, 27 plots were sampled in total. The stover components consisted of leaf blade (sepa-rated at the point of the blade meeting the stem), upper stem (all herbage above the 5th node, excluding the leaf blade, husks, silks, rachis and grain) and lower stem (i.e., all herbage above 5 cm over ground level and below the 5th node, excluding the leaf blades; no husks, silks, rachis or grain were present). On each harvest date either the leaves, upper stem or lower stem were manually removed from all plants present in a sub-plot (10.0 m × 3.8 m), weighed for proportion determination, processed through a precision-chop harvester (set to a theoretical chop length of 19 mm; Pottinger Mex VI, Grieskirchen, Austria), and subsequently sub-sampled.Chemical analysisDry matter (DM) concentration was determined by drying samples in an oven with forced air circulation at 98 °C for 16 hours, while duplicate samples were oven dried at 60 °C for 48 hours and ground using a hammer mill (1 mm apertures; Willey mill, PA, USA) prior to chemical analysis. The in vitro digest-ibility indices, chemical composition and protein fractionation of samples was determined as described by Lynch et al.  LYNCH ET AL.: COMPOSITION OF MAIZE STOVER COMPONENTS 207(2014). In addition, hemicellulose was calculated as neutral detergent fibre (NDF) – acid detergent fibre (ADF) and cellulose as ADF – acid detergent lignin (ADL).Statistical analysisThe data were analysed using a model that accounted for harvest date (main plot; n = 3) and stover component (sub-plot; n = 3) within a three replicate block split-plot design. Stover components were har-vested from separate sub-plots to allow for independent samples. All analyses were conducted using Proc GLM procedure (SAS 2004). Treatment means were com-pared using the Fisher’s least significant difference.ResultsHarvest date did not affect (P > 0.05) the DM, NDF, hemicellulose, lignin, ash or crude protein concentration of sto-ver components (Table 1). The cellulose concentration increased (P < 0.05) and the water soluble carbohydrates (WSC) concentration decreased (P < 0.05) with later harvesting.The DM concentration of lower stem was lower (P < 0.01) than the upper stem and leaf components. Leaf had a greater (P < 0.01) in vitro DM digestibility (DMD) and NDF digestibility (NDFD) and a lower WSC concentration (P < 0.001) than upper stem and lower stem. Leaf had a lower (P < 0.01) NDF concentration than lower stem, and tended (P = 0.052) to have a lower NDF concentration than upper stem. The hemicellulose concentra-tion of lower stem was lower (P < 0.05) than the upper stem and leaf components. The cellulose and lignin concentrations of lower stem were greater (P < 0.001) than the other components, while upper stem also had a greater lignin concentration (P < 0.01) than leaf. In addition, leaf had a greater (P < 0.001) crude protein concentration and a lower (P < 0.001) CN proportion than the other components (Table 2).Upper stem contributed a greater (P < 0.001) proportion of total stover and total whole-crop than the other stover components at all harvest dates, while the proportion of all stover components in whole-crop decreased (P < 0.01) with later harvesting.DiscussionComponent effectsThe greater in vitro DMD of the leaf, com-pared to the stem components, primar-ily reflected a lower NDF concentration. Similarly, studies conducted with a range of maize hybrids by Tolera and Sundstøl (1999) and Tang et al. (2008) reported that the greater in vitro DMD for leaf compared to the total stem component reflected lower NDF and ADF concen-trations. However, the present study also indicated that the higher NDFD of leaf also contributed to its greater nutritive value compared to the stem components, likely due to a lower lignin concentration which allowed for increased utilisation of the cell wall carbohydrates. Furthermore, the crude protein concentration of leaf was higher than in the other components, with a lower proportion of indigestible protein, allowing for 3.8 and 4.6 times higher concentrations of utilisable protein at harvest, compared to upper stem and lower stem, respectively.Of the stem components, the lower section generally had a lower in vitro DMD, primarily due to higher NDF and lignin concentrations. The higher WSC concentration of the stem components compared to leaf was as expected, as stem tissues are utilised for the storage of excess 208     IRISH JOURNAL OF AGRICULTURAL AND FOOD RESEARCH, VOL. 53, NO. 2, 2014Table 1. The chemical composition and in vitro digestibility of maize stover components- harvest date effectsComponent (C) Harvest (H) DM1 DMD1 NDFD1 WSC2 NDF2 Hemi2 Cellulose2 Lignin2 Ash2 CP2  Proportion3In stover4 In whole-cropLeaf 7 Sept. 166b 701a 582a 37c,d 667b 316a 329e 22e 90a 150a 300b,c 202b,c 5 Oct. 154b,c 678a,b 605a 23d 696b 319a 357d,e 20e 90a 138a,b 283b,c 156e,f 5 Nov. 190a 631b,c 566a 21d 708b 307a,b 375c,d,e 26d,e 90a 125b 272c 135f             Upper stem 7 Sept. 161b 658a,b,c 349b,c 164a 701b 302a,b 366c,d,e 33c,d,e 42c 44c 416a 280a 5 Oct. 153b,c 560d 365b 110b 769b 325a 405b,c,d 39b,c,d 48b,c 38c 422a 234b 5 Nov. 160b 498e 304b,c 50c,d 807a 312a 452a,b 43b,c 55b 38c 397a 195c,d             Lower stem 7 Sept. 134c 624c 333b,c 147a,b 740a,b 291a,b 408b,c 41b,c 43c 38c 285b,c 192c,d,e 5 Oct. 135c 511d,e 298c 113b 754a,b 270b 437a,b 47b 48b,c 25c 295b,c 165d,e,f 5 Nov. 134c 437f 317b,c 68c 816a 290a,b 465a 61a 54b 38c 330b 162d,e,f             s.e. C 5.0 9.3 16.1 8.5 16.6 8.7 10.1 2.3 1.9 2.5 – 7.0 H 2.9 10.0 17.0 4.8 14.1 3.6 4.7 3.0 1.5 3.1 – 6.3 CxH 8.6 16.2 28.5 14.8 24.4 15.2 17.5 3.9 3.2 6.3 18.7 12.1             Significance C < 0.001 < 0.001 < 0.001 < 0.001 0.018 0.029 < 0.001 < 0.001 < 0.001 < 0.001  < 0.001 H 0.193 0.002 0.304 0.008 0.091 0.979 0.020 0.125 0.076 0.161 – 0.006 CxH 0.201 0.027 0.338 0.042 0.595 0.511 0.776 0.357 0.250 0.542 0.2968 0.2891 g/kg DM = dry matter; DMD = in vitro DM digestibility; NDFD = in vitro neutral detergent fibre digestibility.2 g/kg DM; NDF = neutral detergent fibre; Hemi = hemicellulose; CP = crude protein; WSC = water soluble carbohydrates.3 Proportion that stover component contributes to total stover or whole-crop, gDM/kg DM.4 Analysed without the main effects, as no variation can occur when components are averaged across components.Means (n  =  3) with the same letters within a column are not significantly different (P > 0.05).s.e. = standard error of the mean. LYNCH ET AL.: COMPOSITION OF MAIZE STOVER COMPONENTS 209carbohydrates and for the transportation of assimilate to the kernels (Slewinski 2012). However, this higher concentration of WSC was not substantial enough to negate the differential in in vitro digest-ibility between the components.Harvest dateDelaying harvest reduced the in vitro DMD of the stem components to a greater extent than leaf, reflecting lower increases in the NDF and lignin concentrations in leaf tissue. Similarly, upper stem incurred a lower decrease in in vitro DMD with delayed harvest compared to the lower stem. This is in accord with previous stud-ies on whole maize stover by Hunt, Kezar and Vinande (1989) and Lynch et al. (2012) that reported decreased DMD with delayed harvest was related to increases in the NDF and lignin concentrations in addition to reductions in the WSC concen-tration. The reduction in WSC concentra-tions of the stem components with delayed harvest was due to the transportation of assimilate to the cob component of the whole-plant for kernel-filling (Lynch et al. 2012; Slewinski 2012).Delaying harvest resulted in a decline in the proportion of leaf in the stover, parallel to an increase in the proportion of lower stem. When the declining propor-tion of stover in the maize whole-crop was considered, delaying harvest decreased the leaf proportion in the total plant by 43% between 7 September and 5 November, compared to a decrease of only 16% for lower stem during the same period. Therefore, while the decrease in nutritive value of each individual stover component with delayed harvest partially contributes to the overall reduction in stover value, Table 2. Nitrogen fractions of maize stover components- harvest date effects   Nitrogen fractions (g fraction N/kg N)1Component (C) Harvest (H) AN  B1N  B2N  B3N  CNLeaf  7 Sept.  146  109  199  489  57e 5 Oct.  195  83  187  467  68d,e 5 Nov.  190  103  209  382  116c,dUpper stem  7 Sept.  235  80  104  452  128b,c 5 Oct.  174  112  150  433  138c 5 Nov.  193  50  138  416  202aLower stem  7 Sept.  267  98  84  419  132b,c 5 Oct.  104  115  215  387  179a,b 5 Nov.  190  97  190  307  215as.e.  C  19.3  18.4  22.4  26.5  5.5 H  20.3  22.8  19.3  22.7  15.5 CxH  33.6  31.9  38.8  46.0  9.7      Significance  C  0.683  0.665  0.129  0.098  < 0.001 H  0.242  0.839  0.243  0.140  0.068 CxH  0.094  0.757  0.442  0.804  0.3081AN = Non-protein N; B1N = rapidly degradable true protein; B2N = variably degradable true protein;  B3N = slowly degradable true protein; CN = Unavailable protein.s.e. = standard error of the mean.Means (n = 3) with the same letters within a column are not significantly different (P > 0.05).210     IRISH JOURNAL OF AGRICULTURAL AND FOOD RESEARCH, VOL. 53, NO. 2, 2014results from the present study indicate that the change in the ratio of leaf to lower stem also significantly influenced the nutritive value of stover.While the current study was conducted with one variety during a single growing season, the findings are applicable to the majority of Irish maize production, as commercially selected cultivars are typi-cally also early maturing and, therefore, variability between cultivars grown in Ireland is likely to be relatively modest.Maximising stover nutritive valueThe higher protein concentration and lower decline in digestibility with delayed harvest of the leaf component reflects a higher feed value compared to the lower stem. Thus, maximising the proportion of this component in the harvested for-age relative to the poor-quality lower stem would partially offset the negative influence of the stover component on the whole-crop nutritive value for crops harvested at later maturity. This may be achieved on farms through an increase in cutting height at harvest (Neylon and Kung 2003).Alternatively, the low NDFD of the stem components indicates that a high proportion of hemicellulose and cellulose is unavailable to ruminants at harvest time, and thus there may be an oppor-tunity to improve the value of this ligno-cellulosic material using methods which increase the utilisation of lignin-bound carbohydrates.ConclusionThe stem components of maize stover grown in a marginal climate had a lower nutritive value than the leaf component, and had a larger decrease in digestibil-ity with delayed harvest. The negative influence of the stover component on the whole-crop nutritive value for crops harvested at later maturity may be dimin-ished by increasing the proportion of leaf in the whole-crop and reducing the pro-portion of lower stem.AcknowledgementsFunding for this study was provided under the National Development Plan through the Research Stimulus fund administered by the Department of Agriculture, Food and the Marine (RSF 07 501). We acknowledge the provision of maize seed by Seed Technology Ltd., Ballymountain, Ferrybank, Waterford, Ireland, the input into crop production and ensilage by B. Weldon and Teagasc Grange farm staff, the chemical analyses by Teagasc Grange laboratory staff.ReferencesBlümmel, M., Grings, E. and Erenstein, O. 2013. Potential for dual-purpose maize varieties to meet changing maize demands: synthesis. Field Crops Research 153: 107–112.Cook, D.E. and Shinners, K. 2011. Economics of Alternative Corn Stover Logistics Systems. American Society of Agricultural and Biological Engineers Annual International Meeting, Louisville, Kentucky, USA, pages 4791–4829.Erenstein, O., Blümmel, M. and Grings, E. 2013. Potential for dual-purpose maize varieties to meet changing maize demands: overview. Field Crops Research 153: 1–4.Hunt, C.W., Kezar, W. and Vinande, R. 1989. Yield, chemical composition and ruminal fermentability of corn whole plant, ear, and stover as affected by maturity. Journal of Production Agriculture 2: 357–361.Lascano, G.J. and Heinrichs, A.J. 2011. Effects of feeding different levels of dietary fiber through the addition of corn stover on nutrient utiliza-tion of dairy heifers precision-fed high and low concentrate diets. Journal of Dairy Science 94: 3025–3036.Lynch, J.P., O’Kiely, P. and Doyle, E.M. 2012. Yield, quality and ensilage characteristics of whole-crop maize and of the cob and stover components: harvest date and hybrid effects. Grass and Forage Science 67: 472–487.Lynch, J.P., O’Kiely, P. and Doyle, E.M. 2013. Yield, nutritive value and ensilage characteristics of whole-crop maize, and of the separated cob and stover components – nitrogen, harvest date and cultivar effects. The Journal of Agricultural Science 151: 347–367. LYNCH ET AL.: COMPOSITION OF MAIZE STOVER COMPONENTS 211Lynch, J.P., O’Kiely, P., Murphy, R. and Doyle, E.M. 2014. Changes in chemical composition and digestibility of three maize stover components digested by white-rot fungi. Journal of Animal Physiology and Animal Nutrition 98: 731–738.Neylon, J.M. and Kung, L., Jr. 2003. Effects of cut height and maturity on the nutritive value of corn silage for lactating cows. Journal of Dairy Science 86: 2163–2169.O’Kiely, P. and Maloney, A.P. 1995. Performance of beef cattle offered differing ratios of grass and maize silage. Irish Journal of Agricultural and Food Research 34: 76 (abstract only).SAS. 2004. Version 9.1. SAS Institute Inc., Cary, NC, USA.Slewinski, T.L. 2012. Non-structural carbohydrate par-titioning in grass stems: a target to increase yield stability, stress tolerance, and biofuel production. Journal of Experimental Botany 63: 4647–4670.Tang, S., Tan, Z., Zhou, C., Jiang, H., Jiang, Y. and Sheng, L. 2006. A comparison of in vitro fermen-tation characteristics of different botanical frac-tions of mature maize stover. Journal of Animal and Feed Sciences 15: 505–515.Tang, S.X., Gan, J., Sheng, L.X., Tan, Z.L., Tayo, G.O., Sun, Z.H., Wang, M. and Ren, G.P. 2008. Morphological fractions, chemical composi-tion and in vitro fermentation characteristics of maize stover of five genotypes. Animal 2: 1772–1779.Tolera, A. and Sundstøl F. 1999. Morphological frac-tions of maize stover harvested at different stages of grain maturity and nutritive value of different fractions of the stover. Animal Feed Science and Technology 81: 1–16.Received 3 March 2014

A note on the chemical composition and in vitro digestibility of contrasting stover components of maize grown in climatically marginal conditions and harvested at differing maturities.

This study evaluated the nutritive value of three contrasting components of maize
stover (leaf, upper stem, lower stem) at three harvest dates. The leaf component had a
greater in vitro dry matter digestibility (DMD) and a lower NDF concentration, compared
to the stem components. Delaying harvest reduced the in vitro DMD of the stem
components to a greater extent than leaf, reflecting lower increases in the NDF and
lignin concentrations in leaf tissue. The stem components of maize stover had a lower
nutritive value than the leaf component, and had a larger decrease in digestibility with
delayed harvest.Funding for this study was provided under the
National Development Plan through the Research Stimulus fund administered by the Department of Agriculture, Food and the Marine (RSF 07 501

A note on the chemical composition and in vitro digestibility of contrasting stover components of maize grown in climatically marginal conditions and harvested at differing maturities.

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